Adding more live rock will cause an ammonia spike, but not mess things up. You may have to wait longer to add fish.
Are those brown things moving? They look a lot like flatworms to me. But, it is not the best picture.
Should I add anything to get rid of the algae or just wait for the cycle.
Algea is a necessary part of the system. Never add anything to a marine tank for getting rid of it. unless it is for phosphate/ nitrate control. Still you are better off growing macro algea that will use the nutrients, and keep nuisance algea at bay.
You might think about checking water daily. If you chart it you will be able to see the cycle occur and you will understand what is happening a lot better.